Traditionally, cellular radio network systems were designed to run over frequencies licensed to specific mobile operators. This has been the case both 3G systems such as WCDMA, and indeed also for LTE.
Preparation is ongoing within 3GPP to start sending LTE signals over unlicensed frequencies. In the 5 GHz band, in which Wireless LAN already may operate, there is more than 400 MHz of unlicensed spectrum available in most countries, and while no one will be able to use all 400 MHz at one time, an average subscriber within range of an unlicensed LTE cell might get twice as much spectrum as in the licensed spectrum, according to certain estimates. The use of LTE on unlicensed bands has generally been considered for public places where there is coverage from licensed band LTE operation but where additional capacity would be beneficial, such as indoor cells or outdoor hot spots. The proposed solutions are designed to co-exist with a licensed LTE connection. Unlicensed LTE is therefore named LAA (Licensed Assisted Access), an extra spectrum resource, especially on, for example, the 5 GHz frequency band, which can complement licensed bands. In 3GPP this work has been divided into a first phase/version where LAA supports downlink only operation, and a second phase/version denoted eLAA (Enhanced Licensed Assisted Access) which also allows for uplink operation. Further phases/versions of LAA concepts could add additional functionality in the future. The technology and specifications developed will be a step towards mobile terminals using any kind of spectrum that is available, which is expected to continue in next-generation 5G networks.